Usually, in industries that work with pieces which are cut, once the material coming from a coil has been cut, it is necessary to stack the pieces obtained.
The stacking may be carried out by transporting the pieces until they are positioned on a pallet where centering devices subsequently center them, or otherwise, without the above-mentioned centering devices thus affecting the shape quality of the stack obtained. The first system has been used with pieces that are stacked in a single stack per pallet, and to stack two or three stacks per pallet, but in this case, the stacking speed is reduced and the positions are limited due to the access of the centering devices to the stacking position. The stacking may also be carried out by free fall, such that the material falls freely in some guided systems, allowing the stacking of pieces.
Finally, there are robots in the market that also perform the stacking of pieces upon exiting the cutting machine, said robots are well suited for stacking pieces of small and irregular dimensions, wherein the stacking by means of centering devices is not applicable.
The systems employed by stacking robots require pre-stacking tables, where the pieces exiting the cutting stage are positioned by free fall, and, afterwards, the pieces are lifted by the robot's claws which transport them to the pallet as far as their stacking position, where by repeating this process, a stack of pieces is formed.
Further, in the robot systems, there are two options: the first is to transport the pieces one by one, thus restricting the stacking capacity, since stacking the pieces one by one requires either to wait for the robot to complete a cycle for transporting a new piece to the stack or to have another robot working in the series; and, the second option is waiting for a package of pieces to be created in a centering table to transport the package of pieces to the stacking pallet. During the creation of the package, the centering devices center the pieces to improve the quality of the subsequent stack.
In the robots transporting the package of pieces that have been previously stacked, the claws transporting the packages of pieces and the centering devices of the centering table in which the packages are formed, are manually configured to adapt to the shape of the different pieces.
It takes certain time to perform said manual configuration and to perform a series of in-line tests, therefore, it is usual to have a plurality both of centering devices and of claws tailored to the piece exchanged in the robot, such that it is not necessary to conduct configuration tests. However, this procedure requires a considerable economic investment, as well as having space to store the sets of centering devices and claws.